But Kim Campbell tells The Tennessean that her husband occasionally breaks into a solo air guitar routine, which she says is "kind of fun."

Glen Campbell was diagnosed with the brain-ravaging disease in 2011 and went on a world tour afterward. The singer known for such hits as "Rhinestone Cowboy," ''Wichita Lineman" and "Southern Nights" was moved to a long-term care facility in 2014.

Kim Campbell says he continues to sing, although the words are gibberish and "it's not a melody that we recognize, but you can tell that it's a happy song and he has a song in his heart," so that brings her great comfort.